BORIS Johnson has appointed his Europe adviser David Frost as his national security adviser, replacing Sir Mark Sedwill who will stand down in September.

Sedwill has said it had been “a privilege to serve” as he announced he will stand down from his role as Cabinet Secretary, National Security Adviser and Head of the Civil Service in September, after over 30 years in Government service.

“I am fortunate to have served in some of the most challenging and rewarding jobs in national and international public service under seven prime ministers and in extraordinary times,” he said.

Boris Johnson has nominated Sedwill for a life peerage, and has also asked him to lead a new G7 panel on Global Economic Security as the UK assumes the presidency with a mission to ensure that “the global free trading system on which our economy is based remains fair, competitive and secure”.

The Prime Minister said: “Over the last few years I have had direct experience of the outstanding service that you have given to the Government and to the country as a whole.”

“It has been by any standards a massive contribution – but as PM I have particularly appreciated your calm and shrewd advice.”

“You have also spoken with a unique authority – unusual in a Cabinet Secretary – on international affairs and national security; and as National Security Adviser you have done much to keep this country safe.

“It is therefore great news that you have agreed to continue to serve this country on the international stage, beginning with the UK’s preparations for the G7 summit next year.”

“You have done it all in Whitehall: from Afghanistan to the modernisation of the civil service; from immigration policy to Brexit and defeating coronavirus. After serving for decades with great distinction – and unflappable good humour – I believe you have earned the gratitude of the nation.”

It comes as Downing Street prepares for an overhaul of how the Cabinet Office and Civil Service functions, with Johnson strongly tipped to break up the roles of Cabinet Secretary and National Security Adviser – positions united by his predecessor Theresa May.